Campbell Biology, Chapter 43, Immune System

Pathogen

disease-causing microorganism

macrophage

large phagocyte found in lymph nodes and other tissues of the body. Engulfes rod shaped bacteria

lymphocytes

A type of white blood cell that make antibodies to recognize and respond to infections and pathogens

immune system

The cells and tissues that recognize and attack foreign substances in the body

What is an example of a first line defense for the immune system?

skin, shells

How are immune cells able to distinguish foreign particles from the bodies particles?

Immune cells produce receptor molecules that bind specifically to molecules from foreign cells or viruses to activate defense responses

molecular recognition

the selective binding of a molecular receptor through the interaction between covalently bonded molecules.

What are the two types of molecular recognition within animals?

innate immunity and adaptive immunity

innate immunity

the body's inborn, nonspecific defenses against any pathogen, effective immediately upon exposure to a pathogen

innate immunity barrier defense

skin, mucous membrsne secretions

innate immunity internal defense

phagocytic cells, natural killer cells, antimicrobial proteins, inflammatory response

How does innate immunity function?

Molecular recognition relies on a small set of receptor proteins that bind to molecules or structures that are absent from the animals bodies but common to a group of viruses or microorganisms.

adaptive immunity

Vertebrate specific immunity where defense is mediated by B lymphocytes and T lymphocytes and exhibits specificity, memory, and self-nonself recognition

adaptive immunity humoral response

antibodies defend against infection in body cells

adaptive immunity cellmediated response

cytotoxic cells defend against infection in body cells

In innate immunity, _______________ and ____________ responses rely on ___________common to groups of pathogens

recognition, response, traits

Insects rely on their______________ for physical barrier against the environment

exoskeleton

Lysozyme

enzyme that kills bacteria by breaking down the cell wall

Hemocytes

recognize bacterial cell walls and engulf bacteria by phagocytosis

Phagocytosis

Cell eating

plasmodium

single celled parasite of mosquitoes that causes malaria

antimicrobial peptides

Short proteins that can insert into bacterial membranes causing bacterial death by disrupting their plasma membrane

mucous

a viscous fluid

The mucus barrier defense in adaptive system functions by...

trapping pathogens and other particles

What is the function of saliva, tears, and mucous in the barrier defenses?

a) constantly bathes the surfaces and washes away particles

b) creates hostile environment for pathogens

Toll-like receptor (TLR)

a mammalian recognition protein similar to the Toll protein of insects

neutrophils

wander in search of bacteria in the blood. Ate attracted to infected tissue and engulf and destroy the infection

macrophages

large phagocytic cells which phagocytize foreign substances.

Dendritic Cells

populate tissues, stimulate the development of adaptive immunity

Eosinophils

discharge destructive enzymes to combat parasites

natural killer cells

cells that circulate through the body and detect abnormal array of surface proteins characteristic of viruses infected cells or cancerous cells

do not engulf cells, instead they release chemicals which lead to cell death

apoptosis

the process of programmed cell death. In immune system this destroys B and T cells that have receptors specific to body tissue

interferon

proteins that provide innate defense by interfering with viral infections

complement system

A group of about 30 different proteins that circulate in an inactive form in the blood. When activated, biochemical responses lead to lysis (bursting) of invading cells, as well as inflammatory response

inflammatory response

A reaction to tissue damage caused by injury or infection.

cytokines

signaling molecules that recruit neutrophils to the site of injury or infection

mast cells

immune cells found in connective tissue release histamine at sites if damage

Histamine

a substance that causes vasodilation and increased vascular permeability. This results in erythema and temperature increase

The enhanced blood flow in inflammatory responses causes the accumulation of...

pus

pus

A fluid created by infection consisting of fluid rich white blood cells, dead pathogens, and debris of damaged tissue

septic shock

a serious condition that occurs when an overwhelming bacterial infection affects the body. Characterized by high fever, low blood pressure, and poor circulation through capillaries

Streptococcus pneumoniae

causes pneumonia and meningitis by avoiding destruction within immune system

myobacterium tuberculosis

causes TB. Caused by bacterium growing and reproducing within cells that consume them

Lymphocytes

A type of white blood cell that make antibodies to fight off infections. Made of T cells and B cells

thymus gland

endocrine gland that stimulates red bone marrow to produce T lymphocytes

T cells

Lymphocytes that mature in the thymus.

B cells

lymphocytes that remains mature in the bone marrow

Antigens

Chemical that stimulates B or T lymphocytes to produce antibodies

antigen receptor

proteins on the surface of the T and B cells that bind to an antigen

Epitope

Small, accessible portion of an antigen that can be recognized.

How do epitope/antigens work in adaptive immunity?

The B and T cells engulf and store an epitope (now called an antigen) and with its antigen receptors is able to recognize future pathogens.

heavy chains

the two long polypeptides that compose an antibody. Act as an anchor to the plasma membrane of B cells

light chains

the two short polypeptides of an antibody.

Constant (C) region

amino acid sequence that doesn't change genetically. It connects the heavy chain to the light chain.

Variable (V) region

region at end if the light chain that varies genetically in order to allow different B cells to recept different pathogens

Transmembrane region

The region of the heavy chain that is anchored in the plasma membrane

Disulfide bridge

a disulfide that links the two heavy chains

Antibody

A protein that acts against a specific antigen

How do B cells activate? What does it so when activated?

B cells that encounter pathogens that match their receptor are activated and matured. B cells fight the microbes and reproduce through mitosis, called antibodies. These antibodies will travel the body and counter other pathogens that match this receptor.

immunoglobulins

Secreted antibodies.

major histocompatibility complex molecule

host protein that displays the antigen fragment on the cell surface

T cells differ from B cells by...

The T cells only have two chains

their chains are called alpha chain and beta chain

B cells have heavy and light chains, t cells do not

How do T Cells mature in order to fight pathogens?

T cells must touch cells that have already engulfed a pathogen. An antigen presenting cell uses a MHC molecule to present an epitope to present antigens to the T cell. Once the T cell is presented with the antigen, the T cell is now mature and able to fight pathogens.

antigen presentation

the display of the antigen fragment in an exposed groove of the MHC protein

What are the four major characteristics of adaptive immunity?

1) The immense repertoire of lymphocytes and receptors enables detection of antigens and pathogens never before encountered

2)Has self-tolerance (lack of reactivity of the animals own molecules)

3) Cell proliferation triggered by activation greatly increases the number of B and T cells specific for antigen

4)There are stronger and more rapid response to an antigen encountered previously

How do we get so many combinations of T and B cells if there are only 20000 protein coding genes.

There are different combinations of proteins which code for different receptors.

A receptor light chain is encoded by what segments?

(v) variable segment, (j) joining segment, and (c) constant segment

Recombinase

genetic enzyme which triggers the recombination of specific sequences without the need of co-factors

What happens if immature lymphocytes cannot distinguish self from non-self?

Why does this happen?

lymphocytes would attack the bodies own tissues and cells, thereby damaging and destroying the organism

This occurs when immature/ self-reactive lymphocytes produce receptors similar to those on our body cells and do not go through apoptosis.

What are the four types of T cells?

T helper cells, cytotoxic T cells, suppressor T cells, and memory T cells

effector cells

short-lived cells that take effect immediately against the antigen and any pathogen producing antigen

What do effector cells form in B cells?

plasma cells, which secrete antibodies

What do effector cells form in T cells?

helper T cells and cytotoxic T cells

What do helper T cells do?

They recognize pathogens, train other immune cells, and stimulate cytotoxic T cells

What do cytotoxic T cells do?

They kill and destroy pathogens

T suppressor cells do what?

These cells shut off immune responses.

Memory T cells do what?

Remember antigen and quickly stimulate immune response on reexposure

memory cells

long-lived cells that can give rise to effector cells if the same antigen is encountered later in the organisms life

clonal selection

The proliferation of a B or T cell into a clone of cells in which an antigen selects which lymphocyte will divide to produce a clonal population of thousands of epitope specific cells.

immunological memory

responsible for the long term protection that a prior infection provides against many diseases

primary immune response

the initial adaptive immune response to an antigen which would appear after 10-17 days

first exposure to pathogen

secondary immune response

the adaptive immune response elicited in second or subsequent exposures to a particular antigen. This is more rapid, has greater magnitude, and longer duration.

humoral immune response

The branch of adaptive immunity which involves the activation of B cells and the secretion of antibodies in the blood and lymph

humors

fluid

cell mediated immune response

specialized T cells destroy infected host cells

helper T cell

A type of T cell which activates humoral and cell mediated immune response

Helper T cells assist B cells do what?

They assist and allow B cells to mature

antigen presentation

The process by which an MHC molecule binds to a fragment of an intracellular protein antigen and carries it to the cell surface, where it is recognized by a T cell. These are present in dendritic cells, macrophages, or B cells

Most body cells only have class I MHC molecules, but antigen presenting cells have class I and class II. Why are class II molecules needed?

class II molecules provide a molecular signature by which an antigen-presenting cell is recognized. This distinguishes antigen-present cells from infected cells.

What's the function of antibodies?

Antibodies encounter pathogens and Mark them for inactivation or destruction.

neutralization

Antibodies prevent a virus or toxic protein from binding to their target

Opsonization

tagging a pathogen for phagocytosis by binding an antibody or antimicrobial protein via a neutrophils or macrophage

Complement activation

Antibodies bind to antigen where complement protein deconstructs the cell membrane.

Passive immunity

transfers of antibodies from one individual to another (mother) to provide temporary protection against pathogens (immunity was given to you, antibodies weren't produced by yourself)

active immunity

develops naturally when a pathogen invades the body and elicits a primary or secondary immune response

latency

viruses that remain in the host in an inactive state